Conventionally, a technique for measuring concentration of constituents in blood without invasion of a living body is disclosed. For example, Patent Document No. 1 teaches the following technique. Near infrared light having at least one of wavelengths selected in a range between 780 nm and 1300 nm is irradiated on a human body. Then, an intensity of transmitted light is measured. Based on the intensity of the transmitted light, a concentration of glucose in the human body is detected.
[Patent Document No. 1]
Japanese Patent Application Publication No. H5-176917
However, in the above prior art, at the time of measurement, even when a degree of force for press-contacting a part of the body to be measured is slightly changed, a measured value may be changed. Thus, measurement with high accuracy cannot be performed.